. >> reporter: the city of vallejo was dredging the public marina when they dug something up. something no one expected. something odd said the marina manager. >> i've been here for 2 -- 23 years. >> reporter: the california oysters, although small and not too many, they are sensitive to quality. folks here believe it's a good sign. >> obviously the water is getting better. quality is getting much improved, which is very nice. >> reporter: this has not always been the case. for more than 100 years, a ship operator across the river and legends had it, once in the 1940s, the water caught fire. which combined with the agriculture run off in the apple valley, created some messy water. down river, matthew manages the 112-year-old vallejo yacht club. since they closed and farming practices have improved, that wildlife is returning. >> we get to see the juvenile seal using our harbors for fishing, getting in the salmon is and the strike bass and they don't have a chance. getting them every time. >> there's still a lot of work to be done, but the small critters are making a big smash.